1. Field of the Invention
This invention relates to manufacturing gasoline. It more particularly refers to an improved technique for upgrading relatively low octane number feed stocks to products of substantially higher octane number and therefore of substantially greater economic value.
2. Description of Prior Art
Trace amounts of water used to promote various catalytic reactions, not including production of high octane gasoline components by way of olefination or aromatization, is known to the art. For example, U.S. Pat. No. 3,546,100 teaches restricting the partial pressure of water in contact with a hydrocracking catalyst during hydrocracking of a hydrocarbon compound to within the range of 10 to 130 mm. U.S. Pat. No. 3,649,524 teaches a high temperature reforming process using only 8-20 ppm water.
Somewhat larger amounts of water have been used in high temperature catalytic dehydrogenation of hydrocarbons (U.S. Pat. No. 3,907,921), wherein 25-3000 ppm of water is used; and in hydrodesulfurization of gas oils and cycle oils (U.S. Pat. No. 3,720,602), wherein 5 to 50 percent of water is injected. In the latter patent, the catalyst material used does not include zeolite materials.
The use of large amounts of water, i.e. about 0.5 to about 16 moles water/mole hydrocarbon feedstock, would be expected, based upon the teaching of the art, to destroy conventional porous, siliceous heterogeneous catalysts, such as used in the present method.
U.S. Pat. No. 3,760,024 discloses an aromatization process for a feedstock comprising C.sub.2 to C.sub.4 paraffins and olefins comprising contacting such feedstock with a crystalline aluminosilicate of the ZSM-5 type at a temperature of about 200.degree. to 1400.degree. F., in the absence of added hydrogen, at pressures of about 0 to 1000 psig, and space velocities equivalent to about 0.1 to 500 WHSV. U.S. Pat. No. 3,756,942 discloses contacting a feedstock having a boiling range of C.sub.5 to those fractions wherein at least 50 volume percent boils no higher than 250.degree. F., with a crystalline aluminosilicate zeolite of the ZSM-5 type at a space velocity equivalent to about 1 to 15 WHSV, a pressure up to about 35 atmospheres and a temperature of about 650.degree. to 1500.degree. F. No water is used in either of these methods.